Hey Jim I don't have anything to back up my Posties claim except for anecdote: When I investigated the High Sheriff of Hartford County, CT, for shaking-down his deputies (a long and normalized tradition, that) there was no state actor who would go after him, on account of his political connex. The Chief State's Attorney there and then, one John Bailey (son of John Bailey, brother of US Rep Barbara Kennelly, etc. & soforth), opened an "investigation" that literally dragged on for years; an obvious slow-walk/coverup. (Bailey at one point go so mad about my constant harping about this that he called me at home on a Sunday to berate me personally; good times!).
Anyway, couple years into it the Feds finally take an interest. It's still two more years before the charges come but, yup, Mail Fraud.
There was another investigation up there of a connected city computer contractor, and there have been several more recently down here 'round Baltimore. They're greatly outnumbered by many other LE orgs but, in my (admittedly limited) experience, Postal Inspectors are fraud specialists.
It's probably a case of confirmation bias. The sorts of cases that interest me often involve politically-wired folks who other LE outfits may be conflicted with in terms of investigating them.
But it's a good story anyway so I ain't checking it.